Post on 25-Dec-2015
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Humans and the Microbial WorldChapter 1
Current Microbial ThreatsMeasles (vaccine preventable)
Polio (vaccine preventable)
Whooping cough (pertussis; vaccine preventable)
Severe acute respiratory syndrome (SARS CoV)
Malaria
Yellow fever virus
West nile virus
Tuberculosis
Human immunodeficiency virus (HIV; AIDS)
Hepatitis C virus
Multidrug-resistant Staphylococcus aureus
H5N1 Avian Influenza
Nipah virus
Hospitals
1.1 The World of Microorganisms
Spontaneous Generation: Life from nonliving materials
Disproved by Francesco Redi in late 1600s
Showed that worms which appeared on rotting meat were from fly eggs
Disproved again by Louis Pasteur in mid 1800s
Showed that appearance of microbes in sterilized media was from air-borne bacteria
Showed that sterilized materials remained sterile if kept isolated from the external environment
1.2 Microbiology: A Human Perspective
Microorganisms cannot be seen without the aid of a microscope
There are more than 200,000 known microbes
Exist in virtually any environment that has water
Exhibit tremendous biodiversity
Compose the largest biomass group of living organisms
Nitrogen fixation: Converting atmospheric nitrogen (gas) to biomolecules (e.g., nucleic acids, amino acids)
Oxygen production: Convert carbon dioxide to molecular oxygen (O2)
Degradation of organic materials
Gastrointestinal tract
Sewage treatment plants
Vital activities of microorganisms
Food production: bread, beer
Bioremediation: decontamination of hazardous wastes
Useful products: ethanol fuel, antibiotics, amino acids
Genetic engineering: pharmaceuticals, vaccines
Genomics: genome sequencing permits understanding of disease mechanisms
Applications of Microbiology
Infectious diseases have killed more people than all wars and natural disasters combined
Outbreaks have changed the course of history
Notable pandemics
Spanish Flu (1918-1919): 50 million global deaths
Smallpox (middle ages): >100 millions deaths (est.)
Plague (1300s-1800s): >100 million deaths (est.)
Introduction of European diseases killed 30 to 40 million Native Americans (est.)
Vaccines have dramatically decreased the incidence of infectious diseases, especially in children
Medical microbiology
Re-emergence of “Old” Infectious Diseases
Colorado has one of the lowest childhood vaccination rate in the U. S.
Cases of whooping cough have increased in the last few years
Many microbes have evolved antibiotic resistance
Medical microbiology (cont.)
Emerging infectious diseases
As humans encroach upon wild habitat, new infectious agents (microbes) are discovered
These agents are typically hosted by animals and are termed zoonotic agents
Medical microbiology (cont.)
Agent Host Disease
Ebola virus Bats Ebola hemorrhagic fever
SARS virus Bats Severe acute respiratory syndrome
Sin Nombre virus Deer mouse Hantavirus cardiopulmonary syndrome
Nipah virus Bats Nipah encephalitis
Dengue virus Mosquitos Dengue fever; Dengue hemorrhagic fever
Machupo virus Vesper mouse Bolivian hemorrhagic fever
Avian influenza viruses
Various birds Influenza
Some recently discovered agents and their animal hosts
1.3 The Microbial World
Bacteria
Procaryotes (no organelles)
Most have rigid cell walls composed of peptidoglycan
Archaea
Similar to bacteria, but no peptidoglycan
Often found in extreme environments (temperature, pH, high salt, etc.)
Eucarya
Complex organelles
Larger than bacteria and archaea
Members
Algae (photosynthesis)
Fungi (single and multicelluar)
Protozoa
Nomenclature
Genus is capitalized
Species is not
Both are italicized
Example: Yersina pestis
1.4 Viruses, Viroids, and PrionsViruses
Not considered living; they are complex macromolecules composed of nucleic acids and proteins (some have lipids)
Noninfectious viruses are said to be inactivated; you cannot “kill” a virus (since they are not considered living organisms)
Obligate intracellular parasites
Tend to be species-specific
Reside in a reservoir host in which they cause limited pathology or are chronic
Disease usually occurs when the virus “jumps” species
Deer mice permanently host Sin Nombre hantavirus without pathology (disease)
Humans infected with SNV often develop hantavirus cardiopulmonary syndrome
Viroids
Composed of RNA
Smaller than viruses
Rely on other viruses to replicate
Best characterized in plants
Prions
Composed of proteins only
Cause neurological disease, termed spongiform encephalopathy
Can be transmitted to humans from some animals (e.g. “mad cow”)